Isolation and Identification of Gluconobacter cerinus in Honey and Its in Vitro Alcohol Utilization Ability

This study aimed to isolate probiotics with the ability to utilize alcohol from honey and conduct whole-genome sequencing analysis on the selected strains.

The isolates were identified taxonomically by physiological and biochemical tests, 16S rDNA sequencing, and phylogenetic tree construction. Their probiotic characteristics were evaluated through hemolysis, gelatinase activity, nitrate reduction and decarboxylase, antibiotic sensitivity, autoaggregation and hydrophobicity tests. Meanwhile, their abilities to utilize ethanol at different concentrations was compared to explore their in vitro alcohol-degrading activity.

Strain P-2, isolated from honey, was identified as Gluconobacter cerinus P-2, belonging to the genus Gluconobacter. The strain showed neither hemolytic nor gelatinase activity, could not reduce nitrate, and did not decarboxylate amino acids to produce amines. Its autoaggregation capacity was as high as 82.13%, and its hydrophobicity was 37.74%. The survival rate was 77.96% in acidic conditions (pH 3) and 88.76% in the presence of 0.3% bile salts. This strain was susceptible to several antibiotics. After 30 minutes of culture at 37 ℃, the utilization rates of 4% and 20% ethanol by 16 mg of G. cerinus P-2 were 61.49% and 36.43%, respectively, which increased to 100% and 63.38%, respectively, after 1.5 hours. Whole-genome sequencing revealed that the genome size of strain P-2 was 3.17 Mb with an average GC content of 55.62%. Gene ontology annotation indicated that strain P-2 had good metabolic capacity and biofilm-forming capacity, and Clusters of Orthologous Groups of Proteins (COG) annotation revealed that strain P-2 had strong transport and metabolic capabilities, without toxic or pathogenic properties and with good autoaggregation properties. Probiotic prediction suggested a probability of over 99% for being a probiotic strain.

G. cerinus P-2 can accelerate the breakdown of ethanol in the human body, showing promising prospects for probiotic applications.